Mixture of hyaluronic acid and phospholipid prevents adhesion formation on the injured flexor tendon in rabbits

Dipalmitoyl phosphatidylcholine, a highly surface-active polar lipid, has been implicated as a potential boundary lubricant for synovial joints. We examined the effects of dipalmitoyl phosphatidylcholine on the flexor tendon and its protective effect against postoperative adhesion in two experimental steps. First, the flexor digitorum fibularis and the distal pulley of rabbits were set for a friction test. The test was performed with saline solution, sodium hyaluronate, or a mixture of dipalmitoyl phosphatidylcholine and sodium hyaluronate as the lubricant. The friction coefficient was significantly lower with the mixture of dipalmitoyl phosphatidylcholine and sodium hyaluronate than with saline solution or sodium hyaluronate. We concluded that the decreased friction coefficient indicates that dipalmitoyl phosphatidylcholine could complement the boundary-lubricating ability of the tendon. In the second experiment, we used an experimental adhesion model of the flexor digitorum fibularis in the rabbit. During the operation, either saline solution, sodium hyaluronate, or a mixture of dipalmitoyl phosphatidylcholine and sodium hyaluronate was injected into the tendon sheath. The specimen was sent to another tester, and the work required to tear off the adhesion was measured. The work required was significantly greater for the tendons that had been injected with saline solution than for those given injections of dipalmitoyl phosphatidylcholine and sodium hyaluronate. Our findings suggest that dipalmitoyl phosphatidylcholine plays an important role in the boundary lubrication of the tendon and that after tendon injury, the administration of a mixture of dipalmitoyl phosphatidylcholine and sodium hyaluronate may improve tendon lubrication and prevent adhesion formation.